> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prudra.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# MPP payments

> The IETF Monetization Payment Protocol — on-chain Tempo transactions with standard HTTP auth headers.

## MPP payments

MPP (Monetization Payment Protocol) is an IETF Internet Draft that uses standard HTTP authentication headers to carry payment credentials. Unlike x402, where the agent signs off-chain and the server settles, MPP requires the agent to send a real on-chain transaction first, then prove it by passing the transaction hash to the server.

MPP settles on the Tempo blockchain using USDC.e. It uses the standard `WWW-Authenticate` and `Authorization` HTTP headers, making it compatible with standard HTTP authentication libraries.

## The challenge and response headers

**Challenge (in 402 response):**

```
WWW-Authenticate: Payment
  id="ch_abc123",
  realm="your-api.com",
  method="tempo",
  intent="charge",
  request="eyJhbW91bnQiOiIxMDAwMCI..."
```

The `request` field is a base64url-encoded JSON object containing payment details (amount, recipient address, chain ID). The `id` field is an HMAC-SHA256 of all challenge parameters — used to verify the challenge wasn't tampered with.

**Agent response (in re-submission):**

```
Authorization: Payment eyJpZCI6ImNoX2FiYzEyMyIsInR4SGFzaCI6IjB4YWJjLi4uIiwiZnJvbSI6IjB4QWdlbnQuLi4iLCJjaGFpbklkIjo0MjE3fQ==
```

The `Authorization` header value is a base64url-encoded JSON credential:

```json theme={null}
{
  "id": "ch_abc123",
  "txHash": "0xabc...",
  "from": "0xAgentWallet...",
  "chainId": 4217
}
```

## When to use MPP

| Scenario                        | Recommendation                      |
| ------------------------------- | ----------------------------------- |
| Agents on Tempo using USDC.e    | MPP or dual-protocol                |
| Multi-step workflows (sessions) | MPP (session payments are MPP-only) |
| Maximum compatibility           | Dual-protocol (both x402 and MPP)   |
| Base + USDC agents              | x402 instead                        |

MPP is required for [session payments](/payments/sessions/overview). If you need one payment to cover a multi-step workflow, use MPP.

## Tokens and chains

MPP currently supports:

| Token  | Chain         | Chain ID           |
| ------ | ------------- | ------------------ |
| USDC.e | Tempo         | 4217               |
| USDC.e | Tempo testnet | See testnet config |

## Session payments

MPP supports session payments — one payment covers an entire multi-step workflow. After the first payment, the server issues a session ID. Subsequent requests include the session ID and skip payment verification, all accumulating results in the same vault.

See [Session payments](/payments/sessions/overview) for the full setup.

## Tempo chain specifics

Tempo uses Simplex Consensus — no block reorganisations. Prudra requires only 1 confirmation before considering a Tempo transaction settled. This means MPP payment latency is typically under 2 seconds from the agent's transaction to the server's 200 response.

## Related

* [How MPP works](/payments/mpp/how-it-works) — the Tempo transaction and HMAC verification flow
* [Add MPP to an endpoint](/payments/mpp/add-to-endpoint) — configure payMiddleware for MPP
* [Test MPP payments](/payments/mpp/test) — the MPP agent test script
* [Handle the Authorization header](/payments/mpp/authorization) — parse and validate MPP credentials
* [Session payments](/payments/sessions/overview) — one payment per multi-step workflow